Wiring harnesses have been developed consisting of a group of wires of various lengths and diameters for conveying energy such as electrical current or light signals. Typically, the wires are secured together in a generally cylindrical bundle, such as by cable ties, tubing, lacing or by being helically wrapped by a length of pressure-sensitive adhesive tape. The wiring harness may be separated into a main cable and one or more branch cables, separately secured into bundles. The ends of the wires may be connected to various devices, such as electrical components, printed circuit boards or other wiring harnesses.
Frequently, a wiring harness is provided for use in conveying energy with respect to a support structure, such as the body of a vehicle or a machine. In applications in vehicles such as automobiles, airplanes, boats and the like, or in appliances such as clothes washers and dryers, severe space limitations in thickness are frequently encountered. For example, in constructing a vehicle, such as an automobile, it is necessary to convey electrical power and signals between a source of electrical power and various components of the automobile such as tail lights, a radio, switches, electric motors, door locks and the like. A wiring harness provided to accomplish this is most conveniently routed within the relatively narrow space separating the interior surface of the passenger compartment (i.e., the interior of the headliner) and the external surface of the automobile. This restricts the diameter of and the number of wires contained in a bundled wiring harness.
Conventional bundled wiring harnesses are laborious and expensive to construct and do not lend themselves to automatic assembly and installation techniques, such as provided by robotics, increasing the time and expense required to mount a wiring harness on a support structure Also, such bundled wiring harnesses are not readily adapted for secure mounting on a support structure. Vibration or mechanical shock in the support structure is transmitted to the wiring harness and frequently generates undesirable noise, or damage to the wiring harness.
Flat profile wiring harnesses (such as ribbon cables) have been developed in the past in an attempt to overcome some of the limitations of conventional bundled wiring harnesses. U.S. Pat. No. 2,831,049 to Cabral discloses a wiring harness having a pair of wires mounted within a continuous resilient carrier. The bottom surface of the carrier includes an adhesive coating for securing the carrier to a support structure. However, Cabral exhibits several limitations. Specifically, it fails to provide for one or more branch cables diverted from the main cable. The carrier, although depicted as flexible, is inherently less flexible in the plane containing the wires, than the wires themselves, and thus the flexibility of the wiring harness is inhibited.
U.S. Pat. No. 4,210,773 to Haley et al. represents another attempt to overcome the limitations of conventional bundled wiring harnesses. That patent discloses a flat profile wiring harness constructed by arranging a plurality of wires in a desired pattern on a common flat plane and including at least one branch cable. A bonding agent is applied to wires which solidifies to form the wiring harness with the wires secured by the continuous bonding agent in a fixed spatial relationship within the common flat plane.
Although Haley et al allows for a wiring harness having a branch cable, it still suffers from several inherent deficiencies. The wiring harness completely lacks any means for mounting on a support structure. The process of applying a liquid bonding agent over the full length of the wiring harness is slow and expensive. Further, as in the Cabral patent, the flexibility of the wiring harness within the common flat plane containing the wires is 10 reduced by the solidified bonding agent. In both Cabral and Haley et al, identification of and access to individual wires at intermediate points on the wiring harness may be obstructed or prevented by the continuous carrier about the wires. Finally, if the support structure is a vehicle, the continuous carrier in Cabral or the coextensive bonding agent in Haley et al represents not only an undesirable expense, but undesirable additional weight as well.
U.S. Pat. No. 3,733,428, issued to Fry, discloses a flat profile wiring harness in which a row of wires are fused by their insulation to a thermoplastic backing strip. The backing strip may be continuous, or may be broken into a number of discrete segments fused to straight portions of the wiring harness. However, the wiring harness in Fry does not provide means for mounting the wiring harness on a support structure. And, the backing strip is secured to the wires only over a minor portion of the circumference of the wires.